It's been six years since David Sheppard's life was turned upside down by his encounter with disgraced neurosurgeon Suresh Nair.

He has not been able to return to work as a Qantas Defence Services engineer due to complications from the surgery, and still relies on anti-depressants.

His marriage didn't survive the aftermath of the botched procedure and he now observes, not participates in, his nine-year-old son's life.

There were always risks involved in the spinal fusion surgery Mr Sheppard underwent at Dr Nair's hands in November 2007 after injuring his back at work.

The surgeon warned him of the risks, but assured the then-37-year-old that if all went well he would be back at work in three months. Two years later, when Dr Nair was arrested over the death of a prostitute in November 2009, Mr Sheppard was waiting to see him for yet another consultation at his Derby Street rooms opposite the Nepean Public Hospital in Penrith.

Mr Sheppard didn't know it at the time, but in that two years, Nair had been in serious trouble. He had been suspended for a second time by the NSW Medical Board and had fled his apartment as a second prostitute lay dying inside after an all-night cocaine binge.

Mr Sheppard, meanwhile, was in excruciating pain. But it wasn't until that day in November that he began to wonder if something more than bad luck had affected the outcome of his surgery.

''I remember being in hydrotherapy one day and there was a lady there who had been due to see [Nair] for a procedure a week before he was arrested,'' he recalled. ''She said to me she thanked god every day she saw another surgeon.''

Mr Sheppard is shocked at the fate that befell Suellen Domingues Zaupa and Victoria McIntyre, the two prostitutes who died from cocaine overdoses within nine months of each other after partying with Nair in Elizabeth Bay.

Nair was sentenced three years ago on manslaughter and drug supply charges. But with the disgraced surgeon now on the eve of early release, Mr Sheppard is highly critical of the NSW justice and healthcare systems.

''He's caused a lot of issues in my life and in other people's lives, as well as the deaths of those two women,'' Mr Sheppard said.

''I think the system is too lenient with people who are professionals but can't control themselves.''

It is not clear yet whether Mr Sheppard's injuries were caused by Nair's negligence or by bad luck.

Several patients have contacted Fairfax Media with claims they were worse off following surgery performed by Nair.

But others wrote praising a man they credited with restoring quality to their lives.

Specialists who worked alongside Nair described him as a ''conscientious practitioner'' and a ''reasonably talented'' surgeon.

Patrick Cregan, who was the clinical director of surgery with the South Western Area Health Service at the time Nair worked at Nepean Public Hospital, told Fairfax Media during the criminal court case there were ''often bad outcomes'' in neurosurgery and that it was a '' fairly murky area''.

Mr Sheppard said: ''I am more angry towards the hospital than Nair because they allowed a doctor to continue working and operating even though he had been suspended so many times before, and as a patient I never knew.

''Had I known about his situation I would never have let him do it.''

Mr Sheppard is still waiting on the outcome of his workers compensation claim before going into his own claim against Nepean Private Hospital.

Another former patient of Nair's, Helen Kerner, is also puzzled that he might be getting out of jail so soon.

The surgeon's drill slipped during a delicate but standard procedure and sliced through several nerves in her spine.

''I won't be the same ever again,'' she said, ''but he gets out of jail and he can live a normal life and have fun. All of us patients can't. Not the ones he's mutilated. It's not fair.''